You can either say "when it is present" or just "when present" for the descriptions on these.

Fixed

In the old code, we guaranteed that a <tr> never got appended to a <table>. Do all the supported browsers in master auto-insert the <tbody> for us now? Do we have a unit test verifying that? I see some weak existing tests here and here but don't think they are making sure of this.

I guess you missed my comment

Indeed I forgot you put in that much detail!

According to html5 spec, tbody could be ommited but will be auto-inserted if table has td, th, tr tags.

If so should we ensure that with a test? Is it true for Android 2.x for example?

I will complete my previous comment there.

Basically, you can't use innerHTML property on the table element (only on tbody) in IE6-9 (i suppose at one point innerHTML might have been used like that), plus, in IE6-7 it would protect you from the case like this -

$( "<table/>" ).append( "<tr>...</tr>" );

No need for that now.

Is it true for Android 2.x for example?

There could be situation when table exist with rows and columns without tbody parent - when you use DOM-manipulation methods. But it doesn't matter, since table should be rendered correctly with or without tbody in modern browsers.

Search for tbody though, still necessary, since if user created table through html serialization (like through innerHTML property or defining it directly in html) will create tbody element even if it was omitted, so in order to correctly and consistently manipulate that table, we still need to search for it.

And yeah, i checked it in Android 2.3... and IE6-7, Opera 9, Firefox 3.6 (just to understand genesis of that code-path). They all follow that logic.